Migrate README docs to sphinxdoc

Signed-off-by: martin f. krafft <madduck@madduck.net>
diff --git a/doc/source/usage.rst b/doc/source/usage.rst
new file mode 100644
index 0000000..c87114e
--- /dev/null
+++ b/doc/source/usage.rst
@@ -0,0 +1,38 @@
+=============
+Using reclass
+=============
+For information on how to use |reclass| directly, call ``reclass --help``
+and study the output, or have a look at its :doc:`manual page <manpage>`.
+
+The three options, ``--inventory-base-uri``, ``--nodes-uri``, and
+``--classes-uri`` together specify the location of the inventory. If the base
+URI is specified, then it is prepended to the other two URIs, unless they are
+absolute URIs. If these two URIs are not specified, they default to ``nodes``
+and ``classes``. Therefore, if your inventory is in ``/etc/reclass/nodes`` and
+``/etc/reclass/classes``, all you need to specify is the base URI as
+``/etc/reclass`` — which is actually the default (specified in
+``reclass/defaults.py``).
+
+If you've installed |reclass| from source as per the :doc:`installation
+instructions <install>`, try to run it from the source directory like this::
+
+  $ reclass -b examples/ --inventory
+  $ reclass -b examples/ --node localhost
+
+This will make it use the data from ``examples/nodes`` and
+``examples/classes``, and you can surely make your own way from here.
+
+On Debian-systems, use the following::
+
+  $ reclass -b /usr/share/doc/reclass/examples/ --inventory
+  $ reclass -b /usr/share/doc/reclass/examples/ --node localhost
+
+More commonly, however, use of |reclass| will happen indirectly, and through
+so-called adapters. The job of an adapter is to translate between different
+invocation paradigms, provide a sane set of default options, and massage the
+data from |reclass| into the format expected by the automation tool in use.
+Please have a look at the respective README files for these adapters, i.e.
+for :doc:`Salt <salt>`, for :doc:`Ansible <ansible>`, and for :doc:`Puppet
+<puppet>`.
+
+.. include:: substs.inc